Which cell type is an agranulocyte?

A. Compression of a vein because of muscle contraction: That’s mechanical venous compression (skeletal muscle pump), not vasodilation.
B. An increase in the diameter of a blood vessel: Definition of vasodilation.
C. Contraction of the ventricles which increases ventricular pressure: That describes ventricular systole, not vasodilation.
D. A decrease in the diameter of a blood vessel: That is vasoconstriction, the opposite of vasodilation.

A. Endocardium: The endocardium is the inner endothelial lining of the heart chambers (endothelium + connective tissue), not cardiac muscle, so it does not contain intercalated discs.
B. Parietal pericardium: The parietal pericardium is the outer layer of the serous/fibrous sac surrounding the heart (protective membrane), not muscle tissue, so it lacks intercalated discs.
C. Epicardium: The epicardium (visceral layer of serous pericardium) covers the heart surface and contains connective tissue and fat; it overlies the myocardium but is not the muscle layer itself, so it does not have intercalated discs.
D. Myocardium: The myocardium is the heart’s muscular wall composed of cardiac muscle cells that are connected by intercalated discs (for electrical and mechanical coupling).